The technical portion of the profession of an optician consists in mounting a pair of ophthalmic lenses in a frame selected by a wearer. This mounting comprises three main operations:                acquiring the shape of the bezel of each of the two rims of the eyeglass frame selected by the future wearer, i.e. the shapes of the longitudinal strands of the bezels corresponding generally to the bottoms of the grooves running along the insides of the rims of the frame, and possibly also acquiring the sections of the bezels;        centering each lens, which consists in determining the position that is to be occupied by each lens in the frame so as to be appropriately centered facing the pupil of the eye of the wearer so that the lens acts appropriately in performing the optical function for which it was designed; and        shaping each lens, which consists in machining or cutting away its outline to the desired shape, taking account of the defined centering parameters and, at the end of machining, beveling which consists in making a bevel on the edge face of the lens for the purpose of holding the lens in the bezel included in the frame.        
In the context of the present invention, attention is given in particular to the first operation of acquiring the shape of the bezel in the rims of the selected eyeglass frame.
In practice, the optician begins by feeling the inner outline of each of the two rims of the selected eyeglass frame so as to determine accurately the coordinates of a plurality of points characterizing the shape of the main strand of the bezel of each rim. Knowing the shape of this strand enables the optician to deduce the shape that needs to be presented by the outline of the corresponding lens, after it has been shaped and beveled, so as to enable it to be inserted in the corresponding rim of the frame.
The purpose of this operation is in particular to trace very exactly the bottom of the bezel in the rim being read, so as to enable an accurate digital image to be stored representing the shape of the longitudinal strand of the bezel.
To improve the accuracy with which the lens engages in the corresponding rim of the frame, and as explained in French patent application FR 05/12457 and European patent EP 0 819 967 in the name of the Applicant, it is possible to proceed with another operation of using feeling to acquire the shape of a section of the bezel, so as to be able to determine the way in which the bevel of the ophthalmic lens will engage in the bezel. Acquiring the shape of a section of the bezel serves in particular to calculate the depth to which the bevel of the ophthalmic lens penetrates in the bezel of the eyeglass frame so as to machine the outline of the lens with greater accuracy, taking account of this penetration depth.
Generally, all of the sections of any one bezel present identical geometries; nevertheless, the optician may acquire the shape of a plurality of sections of the bezel in order to take account of the angle of inclination of the bezel due to the curvature of the frame.
The main drawback of performing such an operation of reading sections of the bezel is that it is time-consuming for the optician to implement, in particular when it is necessary to read a plurality of sections in a single bezel.
Another purpose of that operation of acquiring the shapes of bezels in the rims of the selected eyeglass frame is to determine the optimum axial positions for the lenses relative to the front and rear edges of the rims, so that the mounting of the lenses in the frame is of pleasing appearance. For reasons of appearance, provision is generally made to position the front faces of the lenses flush with the front edges of the rims. In practice, this positioning is performed by acquiring the position of the bottom of the bezel relative to the front and/or rear edges of the rims of the frame, at at least one point for each rim.
Nevertheless, for this purpose likewise, this operation is time-consuming to implement.